Horizontal rotary grinding mill with floating load-partition



N. L. HALL March 27, 1962 HORIZONTAL ROTARY GRINDING MILL WITH FLOATINGLOAD-PARTITION 2 Sheets-Sheet 1 Filed Feb. 28, 1961 INVENTOR. %0540 .F

l r w LENE? March 27, 1962 L HALL HORIZONTAL ROTARY GRINDING MILL WITHFLOATING LOAD-PARTITION I oooco oo i u e o o o oo 50 O lo QO OO OOIOOFiled Feb. 28, 1961 United States Patett O 3,e27,104 HORIZONTAL ROTARYGRHNDIN G MILL WHTH FLOATING LOAD-PARTITEON Newton L. Hall, RO. Box 83,Salt Lake City, Utah Filed Feb. 28, 1961, Ser. No. 92,355 4 Clams. (Ci.241-176) This invention relates to horizontal rotary grinding mill andapparatus used for the comminution, processing or classification ofores, centents, and granular materials.

The particular application as noted in the herein specification appliesto the crushing and grinding of ores for the recovery of their mineralcontent, and for the crushing, and grinding of rocks and clinker forcement production.

The horizontal rotary mill has a wide application in the trades due toits serviceable shape, low upkeep and high Capacity, the applicationsbeing also extended for chemical processing, mixing and classification,drying and burning.

The mills are operated With either batch or circulating loads, in a Wetor dry condition, and under a practical speed of 400 feet per minute oftravel for the perimeter of the rotating load, using a grinding medium,the mill load being intermixed with a load of long steel rods,substantially the length of the mill cylinder, or, rods of less thandiametral length, and with or without steel balls ranging from one tofive inches in diameter. The mill load is composed of crushed raw orewith mill pulp plus the grinding media. The mill load to be crushed orground varies from a mine run of ore having been crushed in breakers ofthe jaw or gyratory type, with the ore being passed over a grating orgrizzley removing the undersze which is later reduced in a roll or disccrusher, the product being passed to a primary ball or rod mill forreduction to a screen size of six mesh which is'then passed to asecondary ball mill for fine grinding to less than 200 mesh for screensize, a reduction which makes possible a liberation of the fine mineralcontent of the ore, or a fine size reduction required for a cementrnixture.

This application outlines a Construction wherein the impelling featureto the ball mill load is formed by providing an unattached andindependent fioating loadpartition, a dividing wall as a load partition,extending longitudinally within the cylindrical section of the millshell serving as a rotor to impel a general division of the millinterier With its load to virtually form two semicylindrical loadsections.

The compartment wall division can be formed of various means, as a,collective combination of short length rods extending radially inconsecutive alinement in line with the mill axis, (as described in myco-pending applicationfiled in the United States Patent Ofiice onDecember 16, 1960, Serial No. 76,195) or, as in the herein applicationas a closed face load-partition, and/ or as au open face load-partitionwith the various forms of divided actions within the load beingsubstantially similar.

The` closed face load-partition has a mid-portion of thin thickness orwidth to oil'set excessive weight and to provide an anchorage to thecentral portion embedded in the load to hold the load-partitionconcentrically to the mill cylinder and to provide an anchorage toprevent the load-partion from striking the mill shell lining, and alsoto effect a cushioning to the action as the exposed lateral ram of theload-partition strikes the load toe T. The reduction of load-partitionweight is a feature of economy in cost of special steels for the wear onthe hard facings and special steels is an expensive item in milloperation. A load-partition of open face not only oiters an additionaleconomy in weight and in cost of steel but it also provides a passagewayin aXial alinement for the mill product in its transit through the mill.

One of the objects of this invention is to provide a crushing andgrinding mill that is rugged and serviceable, is simple of Constructionand contains within itself the essential parts for operation without theincorporation of extraneous parts to effect milling results of highCapacity, and to produce those results efliciently and economically.

Another object is to provide a mill wherein the circulating load canobtain efilcient processing and pass through the rnill in unobstructedtransit.

Another object is to provide a mill structure with parts which can bedetached and altered to a practical eXtent from the exterior of themill.

Another object is to provide a mill wherein the weight of the millstructure, its linings and load are uniformly distributed and balancedin line With the mill length, not only balanced, but having a weightthat is contained within itself and does not requre a duplicate part tobalance or equalize its ofiset or specific weight.

A further object is to provide an open loadpartition wherein thegrinding impact rams can be of wear resisting steel with the connectingbars forrned of common steel.

A further object is to develop a crushing efiect which is absorbed inscreen range to a grinding effect, that is, crushing to grindng, withouta distinction of screen size therebetween.

A further object is to provide a grinding mill With a,

r'loating load-partition wherein the load-partition attainsindiscriminate positions in axial algnment with the mill shell undersuccessive rotations.

Other objects will become apparent as the invention isdisclosed. 1,

In the drawings: I j FIGURE 1 represents a vertical longitudinal'section of a conical mill With'load and a closed face load-partiton,the sectionbeing taken on line 1-1 of FIG. 2 with the load-partitionbeing inmersd in the load partially and all in a static position. r

FIGURE 2 is a cross section of a conical mill with a closed faceload-partition, the section being taken on line' 2-2 of FIG. 1, the loadbeing shown in a static position.

FGURE 3 is a cross section taken on line 3-3 of a FIG. 1, showing theclosed face load-partition in an advanced position over FIG. 2 with theload being under partial action, the main gear, pinon and Operatingshaft for motive power being shown partially.

FIGURE 4 is a side elevation of an open face loadpartition fol-med oftwo lateral impact rams with connecting rods in between.

FGURE 5 is a cross section of an open face loadtaken on line 5-5 of FIG.4 showing a design partition of construction to be made by fornng theimpact rams of wear resisting steel attached to spreader arms of commonsteel, the intervening space between the opposite rams aording an openpassage to the grouud product in passing in an axial direction to themill discharge.

FIGURE 6 is a vertical longitudinal section, similar to FiG. 1, showinga conical grinding mill with open face ioad-partition in vertical andaxial position and alinement, the mill cylinder being shown withoutlifters.

FIGURE 7 is across section taken on line 7 7 of FIG. 6 showing the openface load-partition in a vertical position with the mill load in Outlineunder normal mill rotation.

FEGURE 8 is a cross section taken on line 8-8 of FIG. iS showing theopen face load-partton in a horzon- 4 tal radial position with theexposed impact ram in posi- 3 tion to strike the load toe T and with themill load shown in Outline, the ram being in an advanced position to theload shown in FIG. 7. The mill driving gear and pirion being shownpartially.

The connecting features of the structural mill parts such as bolts,rivets, welds or other means are not shown, the various ccnnectionsbeing made according to well known structural practice.

In the drawings:

FIGURE l is a vertical longitudinal section of the conical mill withunattached closed face load-partition shown partially immcrsed in astatic load, wherein the conical mill shell is noted by the numeral 1,and the steel mill lining as l-a, the feed end coniform head being notedas l-b and the discharge end coniform head as l-c. The mill shell issupported by the feed open trunnion hearing 2, and the discharge opentrunnion bearing 2-a. The feed scoop is noted as 3, with the centraldetachable head as 3-a. The driving gear is noted as 4, the drivingpinion as 5 mounted on the pinion shaft S-, FIG. 3 The mill is operatedby any suitable motive power.

The floating and unattached closed face load-partition is noted as 6with its reduced section or middle portion as 6-a, the enlarged rimportion being noted as 6-b. The load shown in a static position is notedas 7, FIGS. l and 2 with the oversize feed portion as 7-a and theundersize discharge portion as 7-b.

The classification of the load is noted in the cylindrical mill sectionof nniforrn diameter as 7-a'. The open discharge hood is noted as 8. Themill structure rests on the abutments 10 at the feed trunnion and IO-aat the discharge trunnion.

In FIGURE 3 the arrow 9 represents the radial throw produced by the edgeterminal of the load-partition in its partial position advancing tostrike the load toe T in forcible impact.

FIGURE 4 is a side elevation of an open face loadpartition with thesimilar and opposite impact rams being noted as 12 and the spreader barsas 13, with the removable attaching pin as 13-a.

FIGURE 5 is a cross section of an open face loadpartition taken on line5-5 of FIG. 4 showing the design for a method of attachment for theimpact ram 12 to the spreader bar 13.

FIGURE 6 is a vertical longitudnal section of a conical mill, similar toFIG. 1 wherein the conical mill shell is noted by the numeral 1 and themill lining plates as l-a, the open face load-partition being noted as12-13-13-a. The mill load with its diferent classifications is noted as7-a, 7-a', and 7-b. The arrow R' notes the central open space betweenthe cylindrical and conical sections of the mill providing a maximumzone for contact between the different mill actions allowing a freedomof passage of the undersize for classification and discharge through theopen trunnion and from the mill. The discharge grate 8-a is attachedfrom the exterior of the mill and upon its removal provides a millentrance for installation or repair and with its large opening avoidsthe necessity for a manhole entry. Rotary mills present a blindoperation and the ease for inspection and entry for repair ofiers adistinct advantage.

FIGURE 7 is a cross section of a mill taken on line 7--7 of FIG. 6,showing the open face load-partiton in a vertical axial position withthe mill load shown under a normal flow.

FIGURE 8 is a cross section of a mill taken on line 8--8 of FIG. 6showing the mill load under an active rotation with the mill crestbreaking to a sliding cascade and with the open face load-partitionadvanced to a horizontal position to strike the load toe T in forcefulimpact, the opposite ram of the open face load-partition being submergedand held within the load to prevent a radial movement and a meeting ofthe exposed opposite ram With a striking of the mill lining or shell atthe horizontal' position. The load-partition is never free from the loadwith either impact ram being enclosed and sub' merged in the risingportion of the load.

A main driving gear is shown in part as 4 with the driving pinion as 5mounted on the power shaft S-a to offer an Operating speed of rotationgoverned by the nor mal speed of rotation approximately 400 feet perminute of travel measured on the perimeter of the rotating load,- thegeneral average of speed of mill rotation varying according to the millshell load diameter. A mill of Seven feet in diameter and rotatingapproximately 20 revolutions per minute will produce a proper cascade tothe mill load action. The mill lining plates will wear and cause alarger mill diameter producing an enlarged circumference to the load andrequiring an adjustment of mill speed to maintain the practical speed ofrotation.

The horizontal rotary grinding mill cylinder with its several parts,plus the grinding elements such as ball or rod, floating load-partition,and, under certain milling practices, the oversize ore, can form themilling apparatus.

Similar reference characters refer to similar parts in all of the views.

In operation:

The conical type of grinding mill possesses the merit of affording aclassification of the load during the erushing action.

The rotating cones have a natural action of classification equal to ascreening action and the cylindrical section with its uniform diameter,has a natural action to concentrate the oversize towards the perimeterof the load, features which are provided by the shape and form of themill cylinders and acting without the use of any extraneous featuressuch as a screen or grate within the mill cylinder.

The mill lining plates l-a, FIG. 2 are shown with lifters l-' andwithout lifters in FIGS. 1 and 3. Mills being started for rotationpossess a sluggish inertia and the loads of certain compositions requireextra lifters to grip the load and place it in full rotation. Otherloads have a density and weight that overcomes a slipping of the loadover the mill lining.

A large variety of grinding media may be used but the common steel ballfrom one to five inches in diameter will meet most requirements. In aconical mill the undersize of ball and load tends to follow the interiersurface of the mill shell and towards the apex of the cone. The oversizetends to move towards the load zone of greater diameter and to thecylindrical mill section.

It is essential that the floating load-partiton type of mill bemaintained, during operation, with the loads on each side of the wallpractically equal and well balanced.

When loads are unequal on either side of the wall, and during rotation,the action of the loads will be to remain in unbalance resulting in theformation of a large ball load on one side and a smaller ball load onthe other side of the wall, the effect being to pass the mill feed tothe side having the smallest ball load Where it will receive the leastgrinding action. When the mill is under rotation an unbalanced load willremain in unbalance from the fact that loads of different size havedifferent actions during rotation and the short time of a singlerotation does not permit the loads to interchange and become balanced.Placing an equalizing slot extending from wall to wall of the mill andplaced midway along the wall length will provide an opening for aportion of the load to freely pass from one compartment to the other andmaintain the load in balance. (Re: United States Letters Patent, filedAug. 22, 1950; Ser. No. 180,752; N. L. Hall, Pat. No.2,653,769-September 29', 1953). The open face load-partition has amici-portion of wall open, and excepting for the spreader bars, entirelyfree for passage of the axial portion of the mill load.

The open face of the load-partition maintains the load as a unit andacts to balance the mill load at all times of rotation.

The cylindrical section of the mill with its several impact actionsprovides the general tendency of the mill action to create a generaldistribution of the load with the oversize towards the enclosing millshell and the undersize towards and alongside of the compartment wall.

As the load-partition rotates, each striking edge of the partition andeach impact ram repeats the impact action following in dual order andthe forces acting to throw the striking edge, or the impact ram, of thepartition against the mill lining and shell are held in restraint by theopposing edge of ram which is held by being embedded in the risingportion of the load so as to hold the partition substantially concentricto the mill shell, the reverse of actions retaining the wall in itscentral position upon the completion of each single load rotation. Whenthe striking rim or impact ram is in position to strike the load toe T,in the direction of the arrow 9 to load toe T, it is practically at themaximum position for radial action and throw extending from the millzenith.

A common circulating ball mill action virtually demands a mill loadingsized to less than 50 percent of the volumetric Capacity of the mill, afrequent loading being at 42 percent Capacity, such a loading beingfrequently limited by the open discharge of the mill trunnion. It isessential that a mill load have suflicient working space for cascadingor over-fall action in the mill space above the load and the extreme ofloading for a circulating load rarely meets a loading of 50 percentCapacity. A further condition being, that an enlarged mill load with itspulp will work against the entering feed at the feed trunnion.

The crushing or milling action of the freely floating and unattachedload-partition is a striking of the load toe with a concentrated weight,actng twice for each revolution of the mill, and is an action resemblinga stamp action within the mill plus any grinding action of attritionfrom' balls which may be contained within the load, whereas, the actionof impact or attrition of the ball load in plain cascade is decidedlydifferent and is one with an insignificant impact action, all of whichis practically within the load cascade. The two actions are dissimilar,for they act upon the load being treated in manners giving differentresults for extractions.

Milling actions of crushing and grinding have been given, by the trade,a Classified term of impact and attrition, but such divisions ofclassication are frequently unjustified.

An impact blow upon a piece will divide one piece into two and in sodoing will also produce extreme fines from the fractured area of thepiece, without any action of attrition.

Similar divisions following will produce fines during the piecereduction, the several impacts being devoid of attritive and a rubbingof peces upon each other. The fines of fracture are always present andnever absent upon impact actions.

The action of the floating load-partition produces results upon the loadwhich may be considered as both of impact and attrition.

The loading of the mill load using the oating and unattachedload-partition preferably should be maintained within 50 and 55 percentof the mill capacity to secure the best results of cone classificationand grading and to secure a mill action of high Capacity, due to thefact principally that the actions in descent of the impact rams areindependent of the size of the mill load, the advantage of the floatingload-partition type can be from 8 to 10 percent above the Capacity ofthe plain ball mill.

I claim:

l. A horizontal rotary grinding mill of the conical mill type of clearinten'or and imperforate shell open at both ends for respective entryand discharge of a transient circulating mill load of discrete material,comprising;

a conical mill shell of cylindrical mid-section and opposi-te coniformend sections based on said cylindrical mid-section enclosing a normalmill load of grinding elements plus mill feed and pulp, said load partlyimmersing a single unattached and independent open face load-partition,said load-partition. being partly submerged in said load and held todiverse positions by said mill load under consecutive mill rotations,said positions being substantially concentric and in axial alinement tosaid mill shell cylindrical section, said load-partition having a widthless than the clear internal diametral width of said mill interior and alongitudinal length less than the length of said cylindrical millsection, said mill being adapted to contain and employ a transientcirculating load of material to be processed or ground.

2. A horizontal rotary grinding mill of the conical mill type of clearinterior and mperforate shell open at both ends for respective entry anddischarge of a transient circulating load of material, comprising;

a conical mill shell of uniform diametral mid-section intermediate toopposite coniform end sections, said mill containing a normal mill loadof material in transit, and grinding elements including a singleindependent floating open face load-partition Unattached to said millinterior, said milling apparatus being adapted to comminute, classify,segregate and discharge said transit load within and from said conicalmill under normal speed of rotation and load saturation.

3. A horizontal rotary grinding mill of clear interior uniform diameter,and imperforate shell open at both ends for respective entry anddischarge of a circulating load of discrete material, to be ground,comprising;

a cylindrical mill shell encl-osing a normal mill load with grindingelements plus mill feed and pulp, said load partly immersing a singleunattached and independcnt closed face load-partition, saidload-partition being partly submerged and held to diverse positions bysaid mill load under consecutive mill rotations, said positions beingsubstantially concentric and in aXial alinement to said cylindrical millshell said load-partition having a width greater than one half of andless than the clear internal diametral width of said mill interior and alongitudinal length less than the length of said cylindrical shell, saidmill being adapted to contain and employ a composite circulating load ofmaterial to be processed or ground.

4. In a horizontal rotary grinding mill of clear interior uniformdiameter, and imperforate shell open at both ends for respective entryand discharge of a circulating load of discrete material, comprising; r

a mill shell of uniform diameter with mill load of grinding elementsplus mill feed and pulp, said grinding elements comprising a grindingball load plus an unattached `and independent oating and rotatableload-partition, said load-partition being' partly im mersed in therising portion of said mill load, said floating and rotatableload-partition being held to positions substantially equal in diametralspaces from either rim or impact ram of said load-partition and saidmill shell lining, said mill being adapted to comminute a circulatingload of discrete material.

References Cited in the file of this patent UNITED STATES PATENTS

